Method and apparatus for transmitting/receiving positioning reference signal in wireless communication system

ABSTRACT

An apparatus and method of processing a positioning reference signal are disclosed. In some embodiments, the method includes determining a narrow-band (NB) positioning reference signal (PRS) bitmap indicating a pattern selecting NB PRS subframes, wherein each NB PRS subframe comprises an NB PRS for positioning an NB user equipment (UE), transmitting, to the NB UE, NB PRS configuration information for the NB UE, the NB PRS configuration information comprising the NB PRS bitmap, determining, by a reference cell and based on the NB PRS bitmap, NB PRS subframes of the reference cell, mapping, by the reference cell, a first NB PRS in the NB PRS subframes of the reference cell, and receiving, from the NB UE and in response to the first NB PRS, a reference signal time difference (RSTD) measurement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of a U.S. patent application Ser. No.15/673,933, filed on Aug. 10, 2017, which claims priority from and thebenefit of Korean Patent Application Nos. 10-2016-0102825, filed on Aug.12, 2016, 10-2016-0103209, filed on Aug. 12, 2016, 10-2016-0126856,filed on Sep. 30, 2016, and 10-2016-0146920, filed on Nov. 4, 2016,which are hereby incorporated by reference in their entirety.

BACKGROUND

1. Field

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting orreceiving a narrow band positioning reference signal.

2. Discussion of the Background

The Narrowband Internet of Things (NB-IoT) concept has been proposed forthe purpose of radio access to the cellular IoT based on anon-backward-compatible variant of Evolved-Universal Terrestrial RadioAccess (E-UTRA).

The NB-IoT may improve indoor coverage and support a large number of lowthroughput devices, and may also enable lower delay sensitivity,significantly decreased device cost, reduced device power consumption,and an optimized network architecture.

The NB-IoT uses a very narrow band, such as a bandwidth corresponding toa single Resource Block (RB), or the like, and thus, physical channels,signals, and the like which have been utilized in E-UTRA (e.g., legacyLong Term Evolution (LTE)) may need to be newly designed. There is aneed for a method of performing positioning by configuring a resourcefor a Positioning Reference Signal (PRS) to be appropriate for a narrowbandwidth, and mapping the sequence of a PRS to the allocated resource.

NB-IoT performs communication only in a Physical Resource Block (PRB)limited in the frequency axis (e.g., a single PRB); thus a larger numberof subframes need to be used to transmit a PRS to secure positioningperformance. However, a detailed method of configuring a time resource(e.g., a subframe) in which an NB-IoT PRS is transmitted has not yetbeen determined.

SUMMARY

A method and apparatus for configuring a Positioning Reference Signal(PRS) for a wireless communication system supporting an NB-IoTenvironment will be described with various example embodiments. One ormore examples describe a method and apparatus for supporting PRSconfiguration in a new form using the time-frequency resourcesconfigurable in an NB-IoT environment, a subframe configuration formapping the PRS, resource allocation in a subframe, a sequenceconfiguration, and the like.

One or more examples describe a method and apparatus for supportingsubframe configuration for mapping the PRS in an NB-IoT environment.

One or more examples describe a method and apparatus for supportingresource allocation in a subframe for NB-IoT environment.

One or more examples describe a method and apparatus for supporting asequence configuration in the NB-IoT system.

According to one or more example embodiments, a positioning referencesignal may be efficiently configured which is less affected byinterference in the NB-IoT environment and is capable of securingexcellent positioning performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a wireless device.

FIGS. 2 and 3 are diagrams illustrating the structure of a radio frameof a 3GPP LTE system.

FIG. 4 is a diagram illustrating the structure of a downlink subframe.

FIG. 5 is a diagram illustrating the structure of an uplink subframe.

FIG. 6 is a diagram illustrating an example of an NB-IoT network.

FIGS. 7A, 7B, and 7C are diagrams illustrating an NB-IoT operation mode.

FIGS. 8 and 9 are diagrams illustrating an RE pattern in which an LTEPRS is mapped to a single resource block pair.

FIG. 10 is a diagram illustrating an Observed Time Difference Of Arrival(OTDOA).

FIG. 11 is a diagram illustrating a control plane and a user plane of anLTE positioning protocol (LPP).

FIGS. 12A, 12B, 12C, 13A, 13B, and 13C are diagrams illustrating an REpattern in an NB-PRS transmission subframe.

FIGS. 14-21 are diagrams illustrating an NB-PRS transmission subframeconfiguration.

FIG. 22 is a diagram illustrating an example of applying muting to anNB-PRS transmission subframe configuration.

FIG. 23 is a flowchart illustrating NB-PRS transmission and receptionoperations.

FIG. 24 is a diagram illustrating the configuration of a processor of awireless device.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments of the present invention will be described morefully hereinafter with reference to the accompanying drawings, in whichexemplary embodiments of the invention are shown. Throughout thedrawings and the detailed description, unless otherwise noted, the samedrawing reference numerals are understood to refer to the same elements,features, and structures. In describing the exemplary embodiments,detailed description of known configurations or functions may be omittedfor clarity and conciseness.

Further, the description herein is related to a wireless communicationnetwork, and an operation performed in a wireless communication networkmay be performed through a process of controlling a network andtransmitting data by a system that controls a wireless network, e.g., abase station (BS), or may be performed in a user equipment (UE)connected to the wireless communication network.

That is, it is apparent that various operations, which are performed forcommunicating with a terminal in a network composed of a plurality ofnetwork nodes including a base station (BS), are executable by the BS orother network nodes excluding the BS. ‘Base station’ may be replacedwith terms such as a fixed station, a Node B, an eNode B (eNB), anaccess point (AP), and the like. Also, ‘Terminal’ may be replaced withterms such as a User Equipment (UE), a Mobile Station (MS), a MobileSubscriber Station (MSS), a Subscriber Station (SS), a non-AP station(non-AP STA), and the like.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.Thus, the present invention is not limited to the foregoing embodimentsand may include all the embodiments within the scope of the appendedclaims. For example, various exemplary embodiments have been describedwith respect to 3GPP LTE or LTE-A systems; however, aspects of theillustrated embodiments may be applied to other mobile communicationsystems.

FIG. 1 is a diagram illustrating the configuration of a wireless deviceaccording to the present invention.

FIG. 1 illustrates a UE 100 that corresponds to an example of a downlinkreceiving device or an uplink transmitting device, and an eNB 200 thatcorresponds to an example of a downlink transmitting device or an uplinkreceiving device. Although not illustrated in FIG. 1, a second UE thatperforms Vehicle-to-Everything (V2X) communication with the first UE 100may exist. The configuration of the second UE is similar to that of thefirst UE 100, and thus detailed descriptions thereof will be omitted.

The UE 100 may include a processor 110, an antenna unit 120, atransceiver 130, and a memory 140.

The processor 110 may process signals related to a baseband, and mayinclude a higher layer processing unit 111 and a physical layerprocessing unit 112. The higher layer processing unit 111 may processthe operations of a Medium Access Control (MAC) layer, a Radio ResourceControl (RRC) layer, or a higher layer. The physical layer processingunit 112 may process the operations of a PHY layer (e.g., processing anuplink transmission signal or processing a downlink reception signal).The processor 110 may control the general operations of the UE 100, inaddition to processing signals related to a baseband.

The antenna unit 120 may include one or more physical antennas, and maysupport MIMO transmission/reception when a plurality of antennas areincluded. The transceiver 130 may include a Radio Frequency (RF)transmitter and an RF receiver. The memory 140 may store informationprocessed by the processor 110, software, an operating system,applications, or the like associated with the operations of the UE 100,and may include elements such as a buffer or the like.

The eNB 200 may include a processor 210, an antenna unit 220, atransceiver 230, and a memory 240.

The processor 210 processes signals related to a baseband, and mayinclude a higher layer processing unit 211 and a physical layerprocessing unit 212. The higher layer processing unit 211 may processthe operations of a MAC layer, an RRC layer, or a higher layer. Thephysical layer processing unit 212 may process the operations of a PHYlayer (e.g., processing a downlink transmission signal or processing anuplink reception signal). The processor 210 may control the generaloperations of the eNB 200 in addition to processing signals related to abaseband.

The antenna unit 220 may include one or more physical antennas, and maysupport MIMO transmission/reception when a plurality of antennas areincluded. The transceiver 230 may include an RF transmitter and an RFreceiver. The memory 240 may store information processed by theprocessor 210, software, an operating system, applications, or the likeassociated with the operations of the eNB 200, and may include elementssuch as a buffer or the like.

The processor 110 of the UE 100 may be configured to implement theoperations of the UE, which have been described in all of theembodiments of the present invention.

An example of a radio frame structure will be described below.

FIGS. 2 and 3 are diagrams illustrating the structure of a radio frameof a 3GPP LTE system.

In a cellular wireless packet communication system, uplink transmissionor downlink transmission is executed in units of subframes. A singlesubframe is defined as a predetermined period of time including aplurality of symbols. The 3GPP LTE standard supports radio framestructure type 1, which is applied to Frequency Division Duplex (FDD),and radio frame structure type 2, which is applied to Time DivisionDuplex (TDD).

FIG. 2 illustrates radio frame structure type 1. A single radio frame iscomposed of 10 subframes, and a single subframe is composed of 2 slotsin the time domain. A time expended for transmitting a single subframeis a Transmission Time Interval (TTI). For example, the length of asingle subframe is 1 ms, and the length of a single slot is 0.5 ms. Asingle slot may include a plurality of symbols in the time domain. Thesymbol may be an Orthogonal Frequency Division Multiplexing (OFDM)symbol in the downlink, or may be a Single Carrier-Frequency DivisionMultiple Access (SC-FDMA) in the uplink, but the symbol may not belimited thereto. The number of symbols included in a single slot may bedifferent based on a Cyclic Prefix (CP) configuration. The CP mayinclude an extended CP and a normal CP. In the case of the normal CP,for example, the number of symbols included in a single slot may be 7.In the case of the extended CP, the length of a symbol is extended andthus, the number of symbols included in a single slot may be 6, which issmaller than the normal CP. When the size of a cell is large, or when achannel state is unstable (e.g., as when a User Equipment (UE) movesquickly or the like), an extended CP may be used to reduce inter-symbolinterference.

In FIG. 2, by assuming the case of a normal CP in a resource grid, asingle slot corresponds to 7 symbols in the time domain. In thefrequency domain, a system bandwidth is defined as integer (N) times aResource Block (RB), a downlink system bandwidth is indicated by aparameter N^(DL), and an uplink system bandwidth is indicated by aparameter N^(DL). A resource block is a resource allocation unit, andmay correspond to a plurality of symbols (e.g., 7 symbols) in a singleslot in the time domain and a plurality of consecutive subcarriers(e.g., 12 subcarriers) in the frequency domain. Each element in aresource grid is referred to as a Resource Element (RE). A singleresource block includes 12×7 REs. The resource grid in FIG. 2 may beapplied equally to an uplink slot and a downlink slot. Also, theresource grid in FIG. 2 may be equally applied to a slot of radio frametype 1 and a slot of radio frame type 2, which will be described asfollows.

FIG. 3 illustrates radio frame structure type 2. Radio frame structuretype 2 is composed of 2 half frames; each half frame may be composed of5 subframes, a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP),and an Uplink Pilot Time Slot (UpPTS). As in radio frame type 1, asingle subframe is composed of 2 slots. The DwPTS is used for initialcell search, synchronization, or channel estimation in a UE, in additionto transmission/reception of data. The UpPTS is used for channelestimation and the UE's uplink transmission synchronization in an eNB.The GP is a period between the uplink and the downlink for removing anyinterference generated in the uplink due to a multi-path delay from adownlink signal. The DwPTS, GP, and UpPTS may be also referred to asspecial subframes.

FIG. 4 is a diagram illustrating the structure of a downlink subframe. Aplurality of OFDM symbols (e.g., 3 OFDM symbols) disposed in the frontpart of a first slot in a single subframe may correspond to the controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a Physical Downlink SharedChannel (PDSCH) is allocated. The downlink control channels used in the3GPP LTE system may include a Physical Control Format Indicator Channel(PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical Hybridautomatic repeat request Indicator Channel (PHICH), and the like. Inaddition, an Enhanced Physical Downlink Control Channel (EPDCCH) may betransmitted to UEs set by an eNB in the data region.

The PCFICH is transmitted in the first OFDM symbol of a subframe, andmay include information associated with the number of OFDM symbols usedfor a control channel transmission in the subframe.

The PHICH is a response to an uplink transmission, and includes HARQ-ACKinformation.

Control information transmitted through the (E)PDCCH is referred to asdownlink control information (DCI). The DCI includes uplink or downlinkscheduling information, or may include other control information basedon various purposes, such as a command for controlling an uplinktransmission power with respect to a UE group or the like. An eNBdetermines an (E)PDCCH format based on the DCI transmitted to a UE, andassigns a Cyclic Redundancy Check (CRC) to that control information. TheCRC is masked with a Radio Network Temporary Identifier (RNTI) based onthe owner or the purpose of the (E)PDCCH. When the (E)PDCCH is intendedfor a predetermined UE, the CRC may be masked with a cell-RNTI (C-RNTI)for the UE. Alternatively, when the PDCCH is for a paging message, theCRC may be masked with a paging indicator identifier (P-RNTI). When thePDCCH is for a system information block (SIB), the CRC may be maskedwith a system information identifier and a system information RNTI(SI-RNTI). To indicate a random access response with respect to a randomaccess preamble transmission of a UE, the CRC may be masked with arandom access-RNTI (RA-RNTI).

FIG. 5 is a diagram illustrating the structure of an uplink subframe. Anuplink subframe may be divided into a control region and a data regionin the frequency domain. A physical uplink control channel (PUCCH)including uplink control information may be allocated to the controlregion. A physical uplink shared channel (PUSCH) including user data maybe allocated to the data region. A PUCCH for a single terminal may beallocated to a resource block pair (RB pair) in a subframe. The resourceblocks included in the RB pair may occupy different sub-carriers withrespect to two slots. This indicates that the RB pair allocated to aPUCCH is frequency-hopped at a slot boundary.

FIG. 6 is a diagram illustrating an example of NB-IoT according to thepresent invention.

From the perspective of Internet of Things (IoT) system, NB-IoT may beconnected to the basic concept of Machine-Type Communication (MTC) orMachine to Machine (M2M) communication, except for the fact that NB-IoTuses a narrow band. NB-IoT may include the exchange of informationbetween NB-IoT UEs 11 and 12 through an eNB 15, excluding humaninteraction, or may include the exchange of information between theNB-IoT UE 11 and 12 and an NB-IoT server 18 through an eNB.

The NB-IoT server 18 may be an entity that communicates with the NB-IoTUEs 11 and 12. The NB-IoT server may execute an NB-IoT-relatedapplication, and may provide an NB-IoT-specific service to the NB-IoTUEs 11 and 12.

The NB-IoT UEs 11 and 12 may be stationary or mobile wireless devicesthat perform NB-IoT communication.

FIGS. 7A, 7B, and 7C are diagrams illustrating an NB-IoT operation modeaccording to the present invention.

NB-IoT may operate in one of three operation modes as shown in FIGS. 7A,7B, and 7C. The three operation modes are a standalone operation mode, aguard-band operation mode, and an in-band operation mode.

FIG. 7A illustrates a standalone operation mode. A spectrum currentlyused in an Enhanced Data Rates for GSM Evolution (GSM/EDGE) Radio AccessNetwork (GERAN) system, which corresponds to one or more Global Systemfor Mobile Communications (GSM) carriers, may be used. For example, oneof the GSM carriers (e.g., a frequency region of a 200 kHz-bandwidth)may be used for NB-IoT.

FIG. 7B illustrates a guard-band operation mode. Resource blocks, whichare not used in a guard-band existing outside the bandwidth of an LTEcarrier, may be used.

FIG. 7C illustrates an in-band operation mode. Resource blocks in thebandwidth of an LTE carrier may be used. For example, one PRB in the LTEbandwidth (e.g., a frequency region of a 180 kHz-bandwidth) may be usedfor NB-IoT.

NB-IoT devices aim to mainly support scenarios in which NB-IoT devicesare operated in buildings or in the basements of buildings in order toprovide a smart metering service, a smart home service, an alarmservice, or the like. This may mean that reliable datatransmission/reception needs to be supported in rooms or basements thatare generally known to be low-performance areas, irrespective of thedeployment of NB-IoT devices. Furthermore, lower power consumption andless complexity need to be maintained, and at the same time, connectionsto multiple NB-IoT devices (50,000 NB-IoT devices from the perspectiveof a single cell) need to be maintained. The requirements of an NB-IoTsystem, which are currently based on the technologies associated withthe GERAN system, are shown in Table 1.

TABLE 1 Performance Objectives Improved indoor MCL (Maximum CouplingLoss) 164 dB coverage Cell Capacity 52574 devices per cell Reducedcomplexity Very cheap based on mass scale deployment or in a disposablemanner Improved power About 10-year battery life efficiency Latency 10seconds for Mobile Autonomous Reporting (MAR) exception reports (ingeneral support relaxed delay characteristics Coexistence GSM/WCDMA/LTE

The present invention describes operations of a system in whichdifferent Positioning Reference Signals (PRS) are defined. The differentPRSs may be referred to as a first PRS and a second PRS. For example,the first PRS may be a PRS used in an NB-IoT environment (hereinafter anNB-PRS), and the second PRS may be a PRS defined in an LTE system(hereinafter LTE PRS). Although the following examples are described byassuming that the first PRS is an NB-PRS and the second PRS is an LTEPRS, the scope of the present invention may not be limited thereto, andexamples of the present invention may be applied when different PRSs aredefined.

Before the examples of the present invention associated with an NB-PRS,an LTE PRS will be described.

An LTE PRS may only be transmitted in a downlink subframe configured fora PRS transmission through higher layer signaling. When both a normalsubframe #0 and a Multicast Broadcast Single Frequency Network (MBSFN)subframe are configured as positioning subframes, the OFDM symbols inthe MBSFN positioning subframe need to use the same Cyclic Prefix (CP)as that of subframe #0. When only an MBSFN subframe is configured as apositioning subframe, the symbols in the corresponding MBSFN subframeconfigured to transmit a PRS need to use an extended CP.

The LTE PRS is transmitted through antenna port (AP) #6.

The LTE PRS cannot be allocated to time/frequency resources to which aPhysical Broadcast Channel (PBCH), and a Primary Synchronization Signal(PSS)/Secondary Synchronization Signal (SSS) are allocated.

The LTE PRS is defined in an environment where a subcarrier space is 15kHz (i.e., Δf=15 kHz).

An LTE PRS sequence may be generated using a Gold-sequence-basedpseudo-random sequence generator as shown in Equation 1 provided below.The pseudo-random sequence generator may be initialized to c_(init) atthe start of each OFDM symbol as shown in Equation 2.

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\mspace{11mu},{{2N_{RB}^{\max,{DL}}} - 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \\{{c_{init} = {{2^{10} \cdot \left( {{7 \cdot \left( {n_{s} + 1} \right)} + l + 1} \right) \cdot \left( {{2 \cdot N_{ID}^{cell}} + 1} \right)} + {2 \cdot N_{ID}^{cell}} + N_{CP}}}{N_{CP} = \left\{ \begin{matrix}1 & {{for}\mspace{14mu}{normal}\mspace{14mu}{CP}} \\0 & {{for}\mspace{14mu}{extended}\mspace{14mu}{CP}}\end{matrix} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$In Equation 1, l denotes a symbol index, n_(s) denotes a slot index, andN^(max,DL)RB denotes the maximum number of downlink resource blocks. InEquation 2, N^(cell) _(ID) denotes a physical layer cell identity. Asshown in Equation 1, the LTE PRS is always generated based on themaximum number of downlink resource blocks (N^(max,DL) _(RB)), althoughthe location and the size of a resource block to which the LTE PRS isactually mapped may vary.

In a downlink subframe configured for LTE PRS transmission, the LTE PRSsequence may be mapped to an RE; the RE's location may be determinedbased on Equation 3 for a normal CP, or may be determined based onEquation 4 for an extended CP.

$\begin{matrix}{{a_{k,l}^{(p)} = {r_{l,n_{s}}\left( m^{\prime} \right)}}{k = {{6\left( {m + N_{RB}^{DL} - N_{RB}^{PRS}} \right)} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antennaports}} \right) \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antennaports}} \right)\end{matrix}m} = 0},1,\ldots\mspace{11mu},{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {m + N_{RB}^{\max,{DL}} - N_{RB}^{PRS}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack \\{{a_{k,l}^{(p)} = {r_{l,n_{s}}\left( m^{\prime} \right)}}{k = {{6\left( {m + N_{RB}^{DL} - N_{RB}^{PRS}} \right)} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antennaports}} \right) \\{2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antennaports}} \right)\end{matrix}m} = 0},1,\ldots\mspace{11mu},{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {m + N_{RB}^{\max,{DL}} - N_{RB}^{PRS}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \\{v_{shift} = {N_{ID}^{cell}{mod}\mspace{14mu} 6}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$In Equations 3 and 4, a reference signal sequence r_(l,ns)(m′) fromEquation 1 may be mapped to a complex-valued modulation symbol a^((p))_(k,l) which is used as a reference signal for an antenna port P. Here,k denotes a subcarrier index, N^(DL)RB denotes a downlink bandwidthconfiguration (e.g., the number of RBs allocated for a downlink),N^(PRS) _(RB) denotes an LTE PRS bandwidth configured by a higher layer,and ν_(shift) denotes a cell-specific frequency deviation value as shownin Equation 5. In Equations 3 and 4, m′ indicates that a PRB for an LTEPRS is located in a frequency region at the center of a bandwidthcorresponding to the maximum number of downlink resource blocks. Thatis, out of the sequences generated based on the maximum number ofdownlink resource blocks according to Equation 1, the only sequenceactually mapped to an RE according to Equations 3 and 4 is a sequencecorresponding to the location of a PRB to which the LTE PRS is mapped.

FIGS. 8 and 9 are diagrams illustrating an RE pattern in which an LTEPRS is mapped to a single resource block pair.

FIG. 8 illustrates examples of the location of an RE to which an LTE PRSis mapped when the number of PBCH antenna ports is 1 or 2 and the numberof PBCH antenna ports is 4 in the case of the normal CP.

FIG. 9 illustrates examples of the location of an RE to which an LTE PRSis mapped when the number of PBCH antenna ports is 1 or 2 and the numberof PBCH antenna ports is 4 in the case of the extended CP.

Subsequently, a subframe configuration associated with an LTE PRS willbe described.

A cell-specific subframe configuration period T_(PRS) and an offsetΔ_(PRS) for LTE PRS transmission may be set according to Table 2 below.T_(PRS) and Δ_(PRS) corresponding to the value of I_(PRS) providedthrough higher layer signaling may also be determined based on Table 2provided below. Accordingly, an LTE PRS transmission subframe isdetermined by a period of T_(PRS) based on a subframe that is APRsdistant from a subframe corresponding to System Frame Number (SFN) 0.Here, the LTE PRS may be transmitted on N_(PRS) consecutive downlinksubframes from the subframe determined by T_(PRS) and Δ_(PRS), and thevalue of N_(PRS) may be provided to a UE through higher layer signaling.That is, each LTE PRS positioning occasion may include N_(PRS)consecutive downlink subframes.

TABLE 2 PRS configuration PRS periodicity PRS subframe offset IndexI_(PRS) T_(PRS) (subframes) Δ_(PRS) (subframes)  0-159 160 I_(PRS)160-479 320 I_(PRS) − 160  480-1119 640 I_(PRS) − 480 1120-2399 1280 I_(PRS) − 1120 2400-4095 Reserved

Table 3 illustrates an example of high layer signaling associated withan LTE PRS configuration.

TABLE 3 -- ASN1START PRS-Info ::= SEQUENCE {  prs-Bandwidth ENUMERATED {n6, nl5, n25, n50, n75, 100, ... },  prs-ConfigurationIndex INTEGER(0..4095),  numDL-Frames ENUMERATED {sf-1, sf-2, sf-4, sf-6, ...},  ..., prs-MutingInfo-r9 CHOICE { po2-r9 BIT STRING (SIZE(2)), po4-r9 BITSTRING (SIZE(4)), po8-r9 BIT STRING (SIZE(8)), po16-r9 BIT STRING(SIZE(16)), ...  } OPTIONAL --Need OP } -- ASN1STOP

An information element from Table 3 may be referred to as PRS-Info, andmay provide information associated with an LTE PRS configuration in acell.

LTE PRS configuration information may include configuration informationof an LTE PRS (e.g., an LTE PRS for the Observed Time Difference OfArrival (OTDOA)) for a single reference serving cell from an LTEpositioning protocol (LPP) layer, that is, a location server. The LTEPRS configuration information may be provided to a UE via an eNB.

The LTE PRS configuration information may include the parameters shownin Table 3. Particularly, a PRS bandwidth (prs-Bandwidth) is a valuewhich corresponds to a bandwidth used for configuring an LTE PRS, and isexpressed as the number of PRBs. The value of a PRS configuration index(prs-ConfigurationIndex) may indicate the value of I_(PRS) as shown inTable 2, and a PRS period (T_(PRS)) and an offset value (Δ_(PRS)) may beset based thereon. The number of downlink subframes (numDL-Frames) mayindicate the number of consecutive subframes (N_(PRS)) in which an LTEPRS is transmitted. PRS muting information provides informationassociated with a PRS muting configuration of a cell, is counted usingan LTE PRS positioning occasion as a unit, and is indicated in bitmapform having a period of T_(REP). When a bit is 0, LTE PRS transmissionis not performed in all downlink subframes in the corresponding PRSpositioning occasion (i.e., the LTE PRS transmission is muted).

FIG. 10 is a diagram illustrating an Observed Time Difference Of Arrival(OTDOA) scheme according to the present invention.

OTDOA is a positioning scheme in which a communication satellitetransmits information to a terrestrial station in LTE. OTDOA is based onmeasuring the difference in arrival time of radio signals transmittedfrom various locations. A plurality of cells transmits referencesignals, and a UE may receive the same. Because the distances betweenthe plurality of cells and the UE are different, the UE will receive thereference signals transmitted from the plurality of cells at differenttimes. The time differences may be recorded by the UE and may betransmitted to a network. The network combines the time differences andthe antenna location information of each cell to calculate the locationof the UE. At least three cells may be measured by the UE, and thosecells may include a reference cell and a neighboring cell.

The difference in time between when the UE receives reference signalsfrom a pair of eNBs is defined as a Reference Signal Time Difference(RSTD). The position measurement is based on measuring an OTDOA for apredetermined reference signal, which is included in a downlink signalreceived from other eNBs.

FIG. 11 is a diagram illustrating a control plane and a user plane of anLTE Positioning Protocol (LPP) according to the present invention.

The positioning technology may consist of an Enhanced Cell ID (E-CID),Observed Time Difference of Arrival (OTDOA), a Global NavigationSatellite System (A-GNSS), and the like, which are capable of supportingpositioning solutions for a control plane and a user plane at the sametime. An LTE network-based positioning function is managed by anEvolved-Serving Mobile Location Centre (E-SMLC)/Secure User PlaneLocation (SUPL) Location Platform (SLP).

Next, examples of the present invention associated with an NB-PRS, whichis distinguished from an LTE PRS, will be described.

An NB-PRS may be defined briefly from four aspects. First, the NB-PRS isdefined by an RE pattern in which the NB-PRS is mapped to a singlePRB-pair (i.e., a single subframe in the time domain and a single PRB inthe frequency domain). Second, the NB-PRS is defined by a sequencegenerated for the NB-PRS. Third, the NB-PRS is defined by the locationand the size of a frequency band in which the NB-PRS is transmitted inthe whole system band. Fourth, the NB-PRS is defined by the locationsand the number of subframes to which the NB-PRS is mapped in the timedomain.

FIGS. 12A, 12B, 12C, 13A, 13B, and 13C are diagrams illustrating an REpattern in an NB-PRS transmission subframe according to the presentinvention.

FIGS. 12A, 12B, and 12C illustrate NB-PRS RE patterns in the case of anormal CP. FIG. 12A illustrates an NB-PRS RE pattern when the number ofPBCH antenna ports is 1 or 2 in an in-band operation mode. FIG. 12Billustrates an NB-PRS RE pattern when the number of PBCH antenna portsis 4 in an in-band operation mode. FIG. 12C illustrates an NB-PRS REpattern in a guard-band operation mode.

FIGS. 13A, 13B, and 13C illustrate NB-PRS RE patterns in the case of anextended CP. FIG. 13A illustrates an NB-PRS RE pattern when the numberof PBCH antenna ports is 1 or 2 in an in-band operation mode. FIG. 13Billustrates an NB-PRS RE pattern when the number of PBCH antenna portsis 4 in an in-band operation mode. FIG. 13C illustrates an NB-PRS REpattern in a guard-band operation mode.

An NB-PRS RE pattern in subframes is the same as an LTE PRS RE patternin subframes. In this instance, in the in-band operation mode, a PRS isnot mapped onto an OFDM symbol where an LTE control region and aCell-specific Reference Signal (CRS) are mapped. In the guard-bandoperation mode, an NB-PRS may be mapped onto all OFDM symbols because anLTE control region and a CRS transmission do not exist.

The RE patterns of the normal CP of FIGS. 12A, 12B, and 12C may beexpressed by Equation 6 or 7, and the RE patterns of the extended CP ofFIGS. 13A, 13B, and 13C may be expressed by Equation 8 or 9.

$\begin{matrix}{{a_{k,l}^{(p)} = {r_{l,n_{s}}\left( m^{\prime} \right)}}{{In}\text{-}{band}}\;{k = {{6 \cdot m} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right) \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)\end{matrix}m} = 0},{{1m^{\prime}} = {{m + {{2 \cdot n_{NPRB}}{Guard}\text{-}{band}k}} = {{{6 \cdot m} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{14mu} 6l}} = 0}}},1,2,3,4,5,{{6m} = 0},{{1m^{\prime}} = {m + {2 \cdot n_{NPRB}}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack \\{{a_{k,l}^{(p)} = {r_{l,n_{s}}(m)}}{{In}\text{-}{band}}{k = {{6 \cdot m} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right) \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)\end{matrix}m} = 0},{{1{Guard}\text{-}{band}k} = {{{6 \cdot m} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{14mu} 6l}} = 0}},1,2,3,4,5,{{6m} = 0},1} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack \\{{a_{k,l}^{(p)} = {r_{l,n_{s}}\left( m^{\prime} \right)}}{{In}\text{-}{band}}{k = {{6 \cdot m} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right) \\{2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)\end{matrix}m} = 0},{{1m^{\prime}} = {{m + {{2 \cdot n_{NPRB}}{Guard}\text{-}{band}k}} = {{{6 \cdot m} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{14mu} 6l}} = 0}}},1,2,3,4,{{5m} = 0},{{1m^{\prime}} = {m + {2 \cdot n_{NPRB}}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack \\{{a_{k,l}^{(p)} = {r_{l,n_{s}}(m)}}{{In}\text{-}{band}}{k = {{6 \cdot m} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{14mu} 6}}}{l = \left\{ {{{\begin{matrix}{4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = 0} \\{1,2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right) \\{2,4,5} & {{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}}} \\\; & \left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)\end{matrix}m} = 0},{{1{Guard}\text{-}{band}k} = {{{6 \cdot m} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{14mu} 6l}} = 0}},1,2,3,4,{{5m} = 0},1} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

In the examples of Equations 6-9, v_(shift) may have one of 6 values,{0, 1, 2, 3, 4, 5}.

In Equations 6 and 8, n_(NPRB) denotes the PRB index of the PRB used forNB-PRS transmission in an NB-IoT environment.

Equations 7 and 9 correspond to mathematical expressions for RE patternsin FIGS. 12A-13C when a UE is not aware of the value of n_(NPRB).

The generation of an NB-PRS sequence according to the present inventionwill be described in detail with reference to Equations 10-12.

When an RE pattern in an NB-PRS transmission subframe according toEquations 6 and 8 is used, an NB-PRS sequence may be generated accordingto Equations 10 and 12. That is, the NB-PRS sequence may be generatedusing the Gold-sequence-based pseudo-random sequence generator inEquation 10. The pseudo-random sequence generator may be initialized toc_(init) at the start of each OFDM symbol as shown in Equation 12. Inthis instance, a UE may generate sequences based on the maximum numberof downlink resource blocks, and out of the generated sequences, only asequence that corresponds to the location of a resource block (n_(NPRB))to which an NB-PRS is mapped may be actually mapped to REs.

When an RE pattern in an NB-PRS transmission subframe according toEquations 7 and 9 is used, an NB-PRS sequence may be generated accordingto Equations 11 and 12. That is, the NB-PRS sequence may be generatedusing the Gold-sequence-based pseudo-random sequence generator inEquation 11. The pseudo-random sequence generator may be initialized toc_(init) at the start of each OFDM symbol as shown in Equation 12. Inthis instance, a UE may not need to generate a sequence based on themaximum number of downlink resource blocks, but may instead generate asequence based on the single resource block to which an NB-PRS is mappedand map the sequences to REs of the single resource block.

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\mspace{11mu},{{2N_{RB}^{\max,{DL}}} - 1}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack \\{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack \\{{c_{init} = {{2^{10} \cdot \left( {{7 \cdot \left( {n_{s} + 1} \right)} + l + 1} \right) \cdot \left( {{2 \cdot N_{ID}^{cell}} + 1} \right)} + {2 \cdot N_{ID}^{cell}} + N_{CP}}}{N_{CP} = \left\{ \begin{matrix}1 & {{for}\mspace{14mu}{normal}\mspace{14mu}{CP}} \\0 & {{for}\mspace{14mu}{extended}\mspace{14mu}{CP}}\end{matrix} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

An NB-PRS transmission PRB may be configured as follows.

The NB-PRS transmission PRB may be a single PRB configured for NB-IoTcommunication. Here, the single PRB index may be n_(NPRB).

The NB-PRS transmission PRB may be one of the LTE PRS transmission PRBs.In this instance, one of the LTE PRS transmission PRBs may be used forNB-PRS transmission. That is, a single PRB may be used for both LTE PRSand NB-PRS transmission, at the same time. In particular, an LTE PRS andan NB-PRS are generated in the same sequence generation scheme and aremapped onto the same location; thus, a PRS sequence transmitted in anNB-PRS transmission PRB (i.e., one of the LTE PRS transmission PRBs) maybe used for an LTE PRS, and may also be used for an NB-PRS.

Alternatively, the NB-PRS transmission PRB may be one of the PRBsremaining after excluding LTE PRS transmission PRBs. That is, the LTEPRS transmission PRB and the NB-PRS transmission PRB may bedistinguished based on the Frequency Division Multiplexing (FDM) scheme.In this instance, the LTE PRS transmission PRB is located in the middleof a downlink system bandwidth; thus, the NB-PRS transmission PRB may belocated in either the low frequency side of the downlink systembandwidth or on the edge of a high frequency side.

Next, an NB-PRS transmission subframe configuration according to thepresent invention will be described in detail.

As described above, in the case of an LTE PRS transmission, an LTE PRSis transmitted in N_(PRS) consecutive downlink subframes. Here, N_(PRS)may be set to one of the values in the set {1, 2, 4, 6}. In the case ofLTE PRS transmission, a plurality of PRBs out of 6, 15, 25, 50, 75, 100PRBs, . . . , and the like may be used according to the systembandwidth.

An NB-PRS is transmitted only in a PRB that is limited in the frequencyaxis (i.e., a single PRB), and thus a larger number of subframes may beused for transmitting an NB-PRS when compared to an LTE PRS, to securepositioning performance. Next, examples of the present inventionassociated with an NB-PRS transmission subframe configuration asoutlined above will be described.

FIG. 14 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to an embodiment of the present invention.

N_(NB-PRS) consecutive downlink subframes may not be used for an NB-PRStransmission, as illustrated in FIG. 14.

To configure NB-PRS transmission subframes, an offset for NB-PRStransmission (i.e., an NB-PRS offset, or simply an offset in FIGS.14-20) and a period of NB-PRS transmission (i.e. an NB-PRS period, orsimply a period in FIGS. 14-20) may be provided to a UE. For example,NB-PRS transmission subframes are determined by the period length of anNB-PRS from a subframe that is an NB-PRS offset distant from apredetermined reference point (e.g., a radio frame corresponding to SFN0).

In the example shown in FIG. 14, an NB-PRS may be transmitted inN_(NB-PRS) consecutive downlink subframes from a subframe determined bythe NB-PRS offset and the NB-PRS period. That is, the start of theN_(NB-PRS) consecutive downlink subframes may be the start of eachNB-PRS period after the NB-PRS offset.

Therefore, the first subframe of each period (NB-PRS period) in which anNB-PRS is transmitted (i.e., a first subframe out of N_(NB-PRS)subframes) may be the first subframe corresponding to a point where eachperiod begins.

In this instance, the value of N_(NB-PRS) may be provided to a UEthrough higher layer signaling. The set of candidate values forN_(NB-PRS) includes {1, 2, 4, 6}, and may also include values greaterthan 6. For example, although the set of candidate values for N_(NB-PRS)may be defined as {1, 2, 4, 6, 12, 16, 24, 36}, the set may not belimited thereto, and may include one or more values greater than thecandidate values.

FIG. 15 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

According to the example shown in FIG. 15, N_(NB-PRS) consecutivedownlink subframes that were obtained by counting subframes excludingpredetermined subframes (or NB-PRS non-transmission subframes) may beused for NB-PRS transmission.

As illustrated in FIG. 15, when it is assumed that subframes that do notinclude a hatch pattern correspond to the predetermined subframes (orNB-PRS non-transmission subframes), and when it is assumed thatsubframes (i.e., subframes including a hatch pattern) excluding thepredetermined subframes (or NB-PRS non-transmission subframes) areconsecutively arranged, N_(NB-PRS) consecutive subframes (e.g., 24consecutive subframes) out of the subframes may be configured as NB-PRStransmission subframes.

That is, the start of the N_(NB-PRS) consecutive downlink subframes maybe the start of each NB-PRS period after an NB-PRS offset. When thesubframe(s) in the start of the NB-PRS period corresponds to thepredetermined subframe (i.e. NB-PRS non-transmission subframe),N_(NB-PRS) subframes may be configured from a subframe remaining afterexcluding the predetermined subframe(s).

Therefore, the first subframe of each period (NB-PRS period) in which anNB-PRS is transmitted (i.e., the first subframe out of N_(NB-PRS)subframes) may be the first subframe after the predetermined subframe(s)(or NB-PRS non-transmission subframe(s)) from a point where each periodbegins.

Here, the predetermined subframe(s) (or the NB-PRS non-transmissionsubframe(s)) may be defined in advance. In this instance, it is assumedthat a UE is aware of the predetermined subframe (or is aware of theNB-PRS non-transmission subframe) based on a previously defined rule oron information indicated by signaling, and thus information indicatingthe predetermined subframe (or the NB-PRS non-transmission subframe) maynot need to be signaled to the UE. However, the scope of the presentinvention does not exclude providing information indicating thepredetermined subframe (or the NB-PRS non-transmission subframe)separately to a UE.

For example, the predetermined subframe (or the NB-PRS non-transmissionsubframe) may be defined as a subframe in which one or more of aNarrowband Physical Broadcast Channel (NPBCH), a Narrowband PrimarySynchronization Signal (NPSS), and a Narrowband SecondarySynchronization Signal (NSSS) are transmitted. This is to prevent acollision between an NB-PRS and an NPBCH, NPSS, or NSSS. That is, anNPBCH that transmits important system information such as MasterInformation Block or the like and an NPSS/NSSS for synchronization aregiven a higher priority than that of an NB-PRS, so that the NB-PRS isnot transmitted in a subframe in which one or more out of the NPBCH, theNPSS, and the NSSS are transmitted. Most REs are used for the NPBCH, theNPSS, or the NSSS in the subframe in which one or more of the NPBCH, theNPSS, and the NSSS are transmitted. Few physical resources onto whichother physical channels or physical signals, such as an NB-PRS, are tobe mapped, exist in the subframe. The scope of the present invention isnot limited by a scheme of defining the predetermined subframe (or theNB-PRS non-transmission subframe) as a subframe in which one or more ofthe NPBCH, NPSS, and NSSS are transmitted. The scope of the presentinvention includes a scheme of excluding a subframe in which apredetermined physical channel or physical signal is transmitted fromNB-PRS transmission subframes (i.e., a scheme of configuring thesubframe as an NB-PRS non-transmission subframe).

As another example, NB-IoT downlink subframes for transmitting a controlchannel (e.g., Narrowband Physical Downlink Control Channel) and aNarrowband Physical Downlink Shared Channel (NPDSCH) in an NB-IoTenvironment may be excluded from an NB-PRS transmission subframe. Thisalso applies to the case that gives priority to control channel and datachannel transmission over NB-PRS transmission in an NB-IoT environment.In this NB-IoT environment, some subframes out of any invalid downlinksubframes may be used for transmitting an NB-PRS. In this instance,invalid downlink subframes are subframes remaining after excluding theNB-IoT downlink subframes used for transmitting a control channel and adata channel.

The predetermined subframe (or the NB-PRS non-transmission subframe) maybe defined as a subframe(s) corresponding to a subframe index 0, 5,and/or 9 in a radio frame. This may be defined based on the location ofa subframe in which an NPBCH, NPSS, and/or NSSS is transmitted in aradio frame. However, the scope of the present invention is not limitedby the subframe index 0, 5, and/or 9, and the scope of the presentinvention includes a scheme of excluding a subframe having apredetermined index value from NB-PRS transmission subframes.

As another concrete example, when NB-IoT downlink subframes fortransmitting a control channel and a data channel in an NB-IoTenvironment are excluded from an NB-PRS transmission subframe,information associated with the excluded NB-IoT downlink subframes maycomply with valid downlink subframe configuration information defined inadvance in the NB-IoT environment. The valid downlink subframeconfiguration information may be included in a “DL-Bitmap-NB-r13”signaling field and may be transmitted through higher layer signalingsuch as an RRC or the like. The signaling field may be a bitmap having alength of 10 or 40. Based on whether a bit value is “1” or “0” in thebitmap, the system determines whether a downlink subframe is a validdownlink subframe or invalid downlink subframe. Some invalid downlinksubframes may be used for transmitting an NB-PRS. In addition, thepredetermined subframe (or NB-PRS non-transmission subframe) may bedefined as an uplink subframe and a special subframe determined by a TDDconfiguration. That is, in a TDD system, NB-PRS transmission subframesinclude a downlink subframe.

In this instance, the value of N_(NB-PRS) may be provided to a UEthrough higher layer signaling. The set of candidate values forN_(NB-PRS) may include {1, 2, 4, 6}, and may further include one or morevalues greater than 6. For example, although the set of candidate valuesfor N_(NB-PRS) may be defined as {1, 2, 4, 6, 12, 16, 24, 36}, this maynot be limited thereto, and may further include one or more valuesgreater than the candidate values.

FIG. 16 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

According to the example shown in FIG. 16, in a duration composed ofN_(NB-PRS) _(_) _(bitmap) _(_) _(length) subframes, the number of NB-PRStransmission subframes (i.e., N_(NB-PRS)) and the locations thereof maybe provided to a UE using a bitmap scheme.

The duration composed of N_(NB-PRS) _(_) _(bitmap) _(_) _(length)subframes begins from the start of every NB-PRS period after an NB-PRSoffset.

Therefore, the first subframe of each period (NB-PRS period) in which anNB-PRS is transmitted (i.e., a first subframe out of N_(NB-PRS)subframes) is a first subframe, which corresponds to a bit value of “1”in the bitmap, from the point where each period begins.

Here, the value of N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be avalue defined in advance as follows. In this instance, it is assumedthat a UE is already aware of the value of N_(NB-PRS) _(_) _(bitmap)_(_) _(length), and thus, information indicating the value of N_(NB-PRS)_(_) _(bitmap) _(_) _(length) may not need to be signaled to the UE.However, the scope of the present invention does not exclude providingthe information indicating the value of N_(NB-PRS) _(_) _(bitmap) _(_)_(length) to the UE.

For example, in FDD and TDD UL-DL configuration 1 to 5, the value ofN_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined as 40 (i.e., 40subframes (40 ms)) in advance. In TDD UL-DL configuration 6, the valueof N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined as 60 (i.e.,60 subframes (60 ms)) in advance. In TDD UL-DL configuration 0, thevalue of N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined as 70(i.e., 70 subframes (70 ms)) in advance. Alternatively, in all cases,the value of N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined as40 (i.e., 40 subframes (40 ms)) or 80 (i.e., 80 subframes (80 ms)) inadvance, irrespective of an FDD and TDD UL-DL configuration.

Alternatively, a plurality of candidate values for N_(NB-PRS) _(_)_(bitmap) _(_) _(length) may be defined in advance, and informationindicating a value to be applied out of the plurality of candidatevalues may be reported to a UE through higher layer signaling.

For example, in FDD and TDD UL-DL configurations 1-5, the candidatevalues for N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined inadvance as 40, 80, 120, and 160; one of the candidate values may then beindicated to a UE. In TDD UL-DL configuration 6, the candidate valuesfor N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined in advanceas 60, 120, 180, and 240; one of the candidate values may then beindicated to a UE. In TDD UL-DL configuration 0, the candidate valuesfor N_(NB-PRS) _(_) _(bitmap) _(_) _(length) may be defined in advanceas 70, 140, 210, and 280; one of the candidate values may then beindicated to a UE. In all cases, the candidate values for N_(NB-PRS)_(_) _(bitmap) _(_) _(length) may be defined in advance as 40, 80, 120,and 160 irrespective of an FDD and TDD UL-DL configuration, and one ofthe candidate values may then be indicated to a UE.

In the examples described above, the scope of the present invention isnot limited to a predetermined value of N_(NB-PRS) _(_) _(bitmap) _(_)_(length), and another value defined in advance may be applied.

In the example shown in FIG. 16, the number of NB-PRS transmissionsubframes and the locations thereof are indicated using a bitmap, andthus the value of N_(NB-PRS) may not be separately provided to a UE.However, the maximum value of N_(NB-PRS) is defined as a value less thanor equal to the value of N_(NB-PRS) _(_) _(bitmap) _(_) _(length). FIG.17 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

In the example shown in FIG. 17, N_(NB)-PRS consecutive downlinksubframes in a predetermined duration composed of L subframes aredefined as NB-PRS transmission subframes. The NB-PRS transmissionsubframes in a single NB-PRS period may be defined by repeating thepredetermined duration composed of L subframes N_(NB-PRS) _(_) _(rep)times.

A duration in which the predetermined duration composed of L subframesis repeated N_(NB-PRS) _(_) _(rep) times, begins from the start of everyNB-PRS period after an NB-PRS offset.

Therefore, in the predetermined duration composed of L subframes, thefirst subframe (i.e., a first subframe from among N_(NB-PRS) subframes)in which an NB-PRS is transmitted is a first subframe corresponding to apoint where the predetermined duration composed of L subframes starts.

Here, L may have a value defined in advance. For example, L may bedefined as 10 (L=10), that is, a single radio frame duration. In thisinstance, it is assumed that a UE is already aware of the value of L,and thus information indicating the value of L may not need to besignaled to the UE. However, the scope of the present invention does notexclude signaling the value of L to the UE.

The value of N_(NB-PRS) _(_) _(rep) may be signaled to the UE. Forexample, candidate values for N_(NB-PRS) _(_) _(rep) may be defined asvalues greater than or equal to 1 and less than or equal to the maximumvalue. One of the candidate values may be provided to the UE throughhigher layer signaling. The maximum value of N_(NB-PRS) _(_) _(rep) maybe determined by L and the value of an NB-PRS period. That is, the valueof N_(NB-PRS) _(_) _(rep) may be determined to satisfy the conditionthat the value of L*N_(NB-PRS) _(_) _(rep) is less than or equal to theNB-PRS period. For example, the set of candidate values for N_(NB-PRS)_(_) _(rep) may include {1, 2, 4, 6}, and may further include one ormore values greater than 6. Alternatively, the value of N_(NB-PRS) _(_)_(rep) may be fixed to one of the candidate values (in other words, thevalue may be set as a value that the UE is already aware of, withoutseparately being signaled to the UE).

In this instance, the value of N_(NB-PRS) may be provided to the UEthrough higher layer signaling. The set of the candidate values forN_(NB-PRS) may be {1, 2, 4, 6}. However, the present invention is notlimited thereto, and may further include one or more values greater thanthe candidate values. Alternatively, the value of N_(NB-PRS) may befixed to one of the candidate values (in other words, the value may beset as a value that the UE is already aware of, without separately beingsignaled to the UE).

FIG. 18 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

In the example shown in FIG. 18, to configure NB-PRS transmissionsubframes, an offset (e.g., an offset from FIG. 18) may be defined thatindicates the start point of an NB-PRS period; a gap (e.g., a gap fromFIG. 18) may also be defined that indicates the start point ofN_(NB-PRS) subframes in an L-subframe duration.

That is, the candidates for NB-PRS transmission subframes may be set byboth a predetermined duration composed of L subframes and N_(NB-PRS)_(_) _(rep), which indicates the number of times that the predeterminedduration is repeated as described in the example shown in FIG. 17. Theexample shown in FIG. 17 illustrates that N_(NB-PRS) consecutivesubframes start from a first subframe in the L-subframe duration. Theexample shown in FIG. 18 illustrates that N_(NB-PRS) consecutivesubframes start from an n^(th) subframe in the L-subframe duration. Thatis, the example of FIG. 17 corresponds to the case in which gap=0 in theexample of FIG. 18.

Also, in the predetermined duration composed of L subframes, the firstsubframe (i.e., the first subframe from among N_(NB-PRS) subframes) inwhich an NB-PRS is transmitted may be the first subframe after the gapfrom a point where the predetermined duration composed of L subframesstarts.

Other features shown in FIG. 18 are the same as the descriptions whichhave been provided for FIG. 17, and thus detailed descriptions thereofwill be omitted.

FIG. 19 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

According to the example shown in FIG. 19, N_(NB-PRS) consecutivedownlink subframes, identified by counting subframes remaining afterexcluding predetermined subframes (or NB-PRS non-transmission subframes)in a predetermined duration composed of L subframes, may be set asNB-PRS transmission subframes. NB-PRS transmission subframes in a singleNB-PRS period may be set by repeating the predetermined durationcomposed of L subframes N_(NB-PRS) _(_) _(rep) times.

As illustrated in FIG. 19, when it is assumed that subframes that do notinclude a hatch pattern correspond to the predetermined subframes (orNB-PRS non-transmission subframes), and subframes (i.e., subframesincluding a hatch pattern) excluding the predetermined subframes (orNB-PRS non-transmission subframes) in the predetermined durationcomposed of L subframes are consecutively arranged, N_(NB-PRS)consecutive subframes (e.g., 6 consecutive subframes) of theconsecutively arranged subframes may be configured as NB-PRStransmission subframes.

A duration in which the predetermined duration composed of L subframesis repeated N_(NB-PRS) _(_) _(rep) times begins from the start of everyNB-PRS period after an NB-PRS offset. When the subframe(s) in the startof the predetermined duration composed of L subframes correspond to thepredetermined subframes (i.e. the NB-PRS non-transmission subframes),N_(NB-PRS) consecutive subframes may be configured from a subframeremaining after excluding the predetermined subframe(s).

Therefore, in the predetermined duration composed of L subframes, thefirst subframe (i.e., the first subframe from among N_(NB-PRS)subframes) in which an NB-PRS is transmitted may be the first subframeafter the predetermined subframe(s) (i.e. the NB-PRS non-transmissionsubframe(s)). from the first subframe corresponds to a point where thepredetermined duration composed of L subframes starts.

Here, the predetermined subframe(s) (or the NB-PRS non-transmissionsubframe(s)) may be defined in advance. In this instance, it is assumedthat a UE is already aware of the predetermined subframe (or the NB-PRSnon-transmission subframe) based on a previously defined rule or oninformation indicated in advance through signaling, and thus informationindicating the predetermined subframe (or the NB-PRS non-transmissionsubframe) may not need to be signaled to the UE. However, the scope ofthe present invention does not exclude transmitting informationindicating the predetermined subframe (or the NB-PRS non-transmissionsubframe) to the UE.

For example, the predetermined subframe (or the NB-PRS non-transmissionsubframe) may be defined as a subframe in which one or more of aNarrowband Physical Broadcast Channel (NPBCH), a Narrowband PrimarySynchronization Signal (NPSS), and a Narrowband SecondarySynchronization Signal (NSSS) are transmitted. This is to prevent acollision between an NB-PRS and an NPBCH, NPSS, or NSSS. That is, anNPBCH that transmits important system information (such as MasterInformation Block or the like) and that transmits an NPSS/NSSS forsynchronization is given a higher priority status than an NB-PRS willhave, so that the NB-PRS is not transmitted in a subframe in which oneor more of the NPBCH, the NPSS, and the NSSS are transmitted. Most REsare used for the NPBCH, the NPSS, or the NSSS in a subframe in which oneor more of the NPBCH, the NPSS, and the NSSS are transmitted. Fewphysical resources onto which other physical channels or physicalsignals, such as an NB-PRS, are to be mapped, exist in that subframe.

The scope of the present invention is not limited to a scheme ofdefining the predetermined subframe (or the NB-PRS non-transmissionsubframe) as a subframe in which one or more of the NPBCH, NPSS, andNSSS are transmitted. The scope of the present invention includes ascheme of excluding a subframe in which a predetermined physical channelor physical signal is transmitted from an NB-PRS transmission subframe(i.e., a scheme of configuring the subframe as an NB-PRSnon-transmission subframe).

As another example, NB-IoT downlink subframes for transmitting a controlchannel (e.g., Narrowband Physical Downlink Control Channel) and aNarrowband Physical Downlink Shared Channel (NPDSCH) in an NB-IoTenvironment may be excluded from an NB-PRS transmission subframe. Thisexample also takes into account a case that gives priority to controlchannel and data channel transmission over NB-PRS transmission in anNB-IoT. environment In an NB-IoT system, some invalid downlink subframesmay be used for transmitting an NB-PRS. These invalid downlink subframesare those subframes remaining after excluding NB-IoT downlink subframesfor transmitting a control channel and a data channel.

In particular, the predetermined subframe (or the NB-PRSnon-transmission subframe) may be defined as subframe(s) correspondingto a subframe index 0, 5, and/or 9 in a radio frame. This may be definedaccounting for the location of a subframe in which an NPBCH, NPSS,and/or NSSS is transmitted in a radio frame. However, the scope of thepresent invention is not limited by the subframe index 0, 5, and/or 9,and the scope of the present invention includes a scheme of excluding asubframe having a predetermined index value from NB-PRS transmissionsubframes.

As another concrete example, when NB-IoT downlink subframes fortransmitting a control channel and a data channel in an NB-IoTenvironment are excluded from an NB-PRS transmission subframe,information associated with the excluded NB-IoT downlink subframes maycomply with valid downlink subframe configuration information defined inadvance in the NB-IoT system. The valid downlink subframe configurationinformation may be included in a “DL-Bitmap-NB-r13” signaling field andmay be transmitted through higher layer signaling such as an RRC or thelike. The signaling field may be a bitmap having a length of 10 or 40.Based on whether a bit value is “1” or “0” in the bitmap, the systemdetermines whether a downlink subframe is a valid downlink subframe oran invalid downlink subframe. Some invalid downlink subframes may beused for transmitting an NB-PRS.

In addition, the predetermined subframes (i.e. the NB-PRSnon-transmission subframe) may be an uplink subframe and a specialsubframe determined by a TDD configuration. That is, in a TDD system, itmay be defined that NB-PRS transmission subframes include a downlinksubframe.

Here, the value of L may be a value defined in advance. For example, Lmay be defined, in advance, as 10 (L=10), that is, as a single radioframe duration. In this instance, it is assumed that a UE is alreadyaware of the value of L, and thus, information indicating the value of Lmay not need to be signaled to the UE. However, the scope of the presentinvention does not exclude signaling the value of L to the UE.

The value of N_(NB-PRS) _(_) _(rep) may be signaled to the UE. Forexample, candidate values for N_(NB-PRS) _(_) _(rep) may be defined asvalues greater than or equal to 1 and less than or equal to the maximumvalue. One of the candidate values may be provided to the UE throughhigher layer signaling. The maximum value of N_(NB-PRS) _(_) _(rep) maybe determined by L and by the value of an NB-PRS period. That is, thevalue of N_(NB-PRS) _(_) _(rep) may be determined to satisfy thecondition that the value of L*N_(NB-PRS) _(_) _(rep) is less than orequal to the NB-PRS period. For example, the set of candidate values forN_(NB-PRS) _(_) _(rep) may include {1, 2, 4, 6}, and may further includeone or more values greater than 6. Alternatively, the value ofN_(NB-PRS) _(_) _(rep) may be fixed to one of the candidate values(i.e., the value may be defined as a value that the UE is already awareof, without separately being signaled to the UE).

In this instance, the value of N_(NB-PRS) may be transmitted to the UEthrough higher layer signaling. The set of the candidate values forN_(NB-PRS) may be {1, 2, 4, 6}. However, the present invention is notlimited thereto, and may further include one or more values greater thanthe candidate values. Alternatively, the value of N_(NB-PRS) may befixed to one of the candidate values (i.e., the value may be defined asa value that the UE is already aware of, without separately beingsignaled to the UE).

FIG. 20 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

In the example shown in FIG. 20, the number of NB-PRS transmissionsubframes (i.e., N_(NB-PRS)) and the locations thereof in apredetermined duration composed of L subframes may be determined using abitmap. NB-PRS transmission subframes in a single NB-PRS period may bedefined by repeating the predetermined duration composed of L subframesN_(NB-PRS) _(_) _(rep) times.

A duration in which the predetermined duration composed of L subframesis repeated N_(NB-PRS) _(_) _(rep) times begins from the start of everyNB-PRS period after an NB-PRS offset.

Therefore, in the predetermined duration composed of L subframes, thefirst subframe (i.e., the first subframe from among N_(NB-PRS)subframes) in which an NB-PRS is transmitted may be a first subframecorresponding to a bit value of “1” in the bitmap from a point where thepredetermined duration composed of L subframes starts.

Here, the value of L may be a value defined in advance. For example, Lmay be defined, in advance, as 10 (L=10), that is, a single radio frameduration. In this instance, it is assumed that a UE is already aware ofthe value of L, and thus, information indicating the value of L may notneed to be signaled to the UE. However, the scope of the presentinvention does not exclude signaling the value of L to the UE.

The value of N_(NB-PRS) _(_) _(rep) may be signaled to the UE. Forexample, candidate values for N_(NB-PRS) _(_) _(rep) may be defined asvalues greater than or equal to 1 and less than or equal to the maximumvalue. One of the candidate values may be provided to the UE throughhigher layer signaling. The maximum value of N_(NB-PRS) _(_) _(rep) maybe determined by L and by the value of an NB-PRS period. That is, thevalue of N_(NB-PRS) _(_) _(rep) may be determined to satisfy that thevalue of L*N_(NB-PRS) _(_) _(rep) is less than or equal to the NB-PRSperiod. For example, the set of candidate values for N_(NB-PRS) _(_)_(rep) may include {1, 2, 4, 6}, and may further include one or morevalues greater than 6. Alternatively, the value of N_(NB-PRS) _(_)_(rep) may be fixed to one of the candidate values (i.e., the value maybe defined as a value that the UE is already aware of, withoutseparately being signaled to the UE).

In the example of FIG. 20, the number of NB-PRS transmission subframesand the locations thereof are indicated using a bitmap, and thus thevalue of N_(NB-PRS) may not be separately provided to the UE. However,the maximum value of N_(NB-PRS) may be defined as a value less than orequal to the value of L.

FIG. 21 is a diagram illustrating an NB-PRS transmission subframeconfiguration according to another embodiment of the present invention.

According to an example of FIG. 21, one or more predetermined durations,each composed of L subframes, are defined for the subframes remainingafter excluding a predetermined subframe (i.e. the NB-PRSnon-transmission subframe) from the entire set of subframes. The numberof NB-PRS transmission subframes (i.e., N_(NB-PRS)) and the locationsthereof are determined based on a bitmap scheme within a predeterminedduration composed of L subframes. NB-PRS transmission subframes within asingle NB-PRS period may be determined by repeating the predeterminedduration composed of L subframes N_(NB-PRS) _(_) _(rep) times.

As illustrated in FIG. 21, when it is assumed that subframes that do notinclude a hatch pattern correspond to the predetermined subframes (i.e.the NB-PRS non-transmission subframes), the number of NB-PRStransmission subframes (i.e., N_(NB-PRS)) and the locations thereof aredetermined based on a bitmap scheme within a predetermined durationcomposed of L subframes out of the set of subframes (i.e., subframesincluding a hatch pattern) remaining after excluding the predeterminedsubframes (or NB-PRS non-transmission subframes). NB-PRS transmissionsubframes within a single NB-PRS period may be determined by repeatingthe predetermined duration composed of L subframes N_(NB-PRS) _(_)_(rep) times.

A duration in which the predetermined duration composed of L subframesis repeated N_(NB-PRS) _(_) _(rep) times, begins from the start of everyNB-PRS period after an NB-PRS offset. When the subframe(s) in the startof the NB-PRS period corresponds to the predetermined subframe (orNB-PRS non-transmission subframe), a duration may be configured byrepeating the predetermined duration composed of L subframes N_(NB-PRS)_(_) _(rep) times from a subframe remaining after excluding thepredetermined subframe(s).

Therefore, the first subframe in which an NB-PRS is transmitted in eachperiod (NB-PRS period) (i.e., the first subframe out of N_(NB-PRS)subframes) may be a first subframe that corresponds to a bit value of“1” in the bitmap at the start point of the predetermined durationcomposed of L subframes, within the predetermined duration composed of Lsubframes, which starts from a first subframe after the predeterminedsubframes (or NB-PRS non-transmission subframes) from the start point ofeach period.

Here, the predetermined subframe(s) (or the NB-PRS non-transmissionsubframe(s)) may be defined in advance. In this instance, it is assumedthat a UE is already aware of the predetermined subframe (or the NB-PRSnon-transmission subframe) based on a previously defined rule or oninformation indicated by signaling, and thus information indicating thepredetermined subframe (or the NB-PRS non-transmission subframe) may notneed to be signaled to the UE. However, the scope of the presentinvention may not exclude separately providing information indicatingthe predetermined subframe (or the NB-PRS non-transmission subframe) tothe UE.

For example, the predetermined subframe (or the NB-PRS non-transmissionsubframe) may be defined as a subframe in which one or more of aNarrowband Physical Broadcast Channel (NPBCH), a Narrowband PrimarySynchronization Signal (NPSS), and a Narrowband SecondarySynchronization Signal (NSSS) are transmitted. This is to prevent acollision between an NB-PRS and an NPBCH, NPSS, or NSSS. That is, anNPBCH that transmits important system information such as a MasterInformation Block (MIB) or the like and that an NPSS/NSSS forsynchronization is given a higher priority than an NB-PRS transmission,so that the NB-PRS is not transmitted in a subframe in which one or moreof the NPBCH, the NPSS, and the NSSS are transmitted. Most REs are usedfor the NPBCH, the NPSS, or the NSSS in the subframe in which one ormore out of the NPBCH, the NPSS, and the NSSS are transmitted; fewphysical resources onto which other physical channels or physicalsignals (such as an NB-PRS) are to be mapped exist in the subframe. Thescope of the present invention is not limited by a scheme of definingthe predetermined subframe (or the NB-PRS non-transmission subframe) asa subframe in which one or more out of the NPBCH, NPSS, and NSSS aretransmitted. The scope of the present invention includes a scheme ofexcluding a subframe in which a predetermined physical channel orphysical signal is transmitted from an NB-PRS transmission subframe(i.e., a scheme of configuring the subframe as an NB-PRSnon-transmission subframe).

As another example, NB-IoT downlink subframes for transmitting a controlchannel (e.g., Narrowband Physical Downlink Control Channel (NPDCCH))and a data channel (Narrowband Physical Downlink Shared Channel(NPDSCH)) in an NB-IoT environment may be excluded from a NB-PRStransmission subframe. This also takes into account the case that givespriority to control channel and data channel transmission over NB-PRStransmission in an NB-IoT system. In such an NB-IoT system, somesubframes out of invalid downlink subframes, which are the subframesremaining after excluding NB-IoT downlink subframes for transmitting acontrol channel and a data channel, may be used for transmitting anNB-PRS.

In particular, the predetermined subframe (or the NB-PRSnon-transmission subframe) may be defined as a subframe(s) correspondingto a subframe index 0, 5, and/or 9 in a radio frame. This may be definedtaking into account the location of a subframe in which an NPBCH, NPSS,and/or NSSS is transmitted in a radio frame. However, the scope of thepresent invention is not limited by the subframe index 0, 5, and/or 9,and the scope of the present invention includes a scheme of excluding asubframe having a predetermined index value from a NB-PRS transmissionsubframe.

As another concrete example, when NB-IoT downlink subframes fortransmitting a control channel and a data channel in an NB-IoTenvironment are excluded from an NB-PRS transmission subframe,information associated with the excluded NB-IoT downlink subframes maycomply with valid downlink subframe configuration information defined inadvance in the NB-IoT system. The valid downlink subframe configurationinformation may be included in a “DL-Bitmap-NB-r13” signaling field andmay be transmitted through higher layer signaling such as an RRC or thelike. The signaling field may be a bitmap having a length of 10 or 40.Based on whether a bit value is “1” or “0” in the bitmap, it isdetermined whether a downlink subframe is a valid downlink subframe oran invalid downlink subframe. Some invalid downlink subframes may beused for transmitting an NB-PRS.

In addition, the predetermined subframes (or NB-PRS non-transmissionsubframe) may be an uplink subframe and a special subframe determined bya TDD configuration. That is, in a TDD system, it may be defined that anNB-PRS transmission subframe is included in the downlink subframes.

Here, the value of L may be a value defined in advance. For example, Lmay be defined in advance as 10 (L=10), that is, as a single radio frameduration. As another example, L may be defined in advance as a valuecorresponding to a multiple of 10, such as L=20 or L=40. In thisinstance, it is assumed that a UE is already aware of the value of L,and thus, information indicating the value of L may not need to besignaled to the UE. However, the scope of the present invention does notexclude signaling the value of L to the UE.

The value of N_(NB-PRS) _(_) _(rep) may be signaled to the UE. Forexample, candidate values for N_(NB-PRS) _(_) _(rep) may be defined asvalues greater than or equal to 1 and less than or equal to the maximumvalue. One of the candidate values may be provided to the UE throughhigher layer signaling. The maximum value of N_(NB-PRS) _(_) _(rep) maybe determined based on the number of the predetermined subframes (orNB-PRS non-transmission subframes), the value L, and the value of anNB-PRS period. That is, the value of N_(NB-PRS) _(_) _(rep) may be setto satisfy the condition that the value of L*N_(NB-PRS) _(_) _(rep) isless than or equal to the number of subframes excluding thepredetermined subframe (or NB-PRS non-transmission subframe) in theNB-PRS period. For example, the set of candidate values for N_(NB-PRS)_(_) _(rep) may include {1, 2, 4, 6}, and may further include one ormore values greater than 6. Alternatively, the value of N_(NB-PRS) _(_)_(rep) may be fixed to one of the candidate values (i.e., the value maybe defined as a value that the UE is already aware of, withoutseparately being signaled to the UE).

In this instance, the value of N_(NB-PRS) may be provided to the UEthrough higher layer signaling. The set of the candidate values forN_(NB-PRS) may be {1, 2, 4, 6}. However, the present invention is notlimited thereto, and may further include one or more values greater thanthe candidate values. Alternatively, the value of N_(NB-PRS) may befixed to one of the candidate values (i.e., the value may be defined asa value that the UE is already aware of, without separately beingsignaled to the UE).

In the example of FIG. 21, the number of NB-PRS transmission subframesand the locations thereof are indicated using a bitmap, and thus thevalue of N_(NB-PRS) may not be separately provided to the UE. However,the maximum value of N_(NB-PRS) may be defined as a value less than orequal to the value of L.

FIG. 22 is a diagram illustrating an example of applying muting to anNB-PRS transmission subframe configuration according to embodiments ofthe present invention.

To perform positioning through a PRS based on an OTDOA scheme, not alleNBs (or cells) need to transmit PRSs at a predetermined point in time.Positioning through a PRS based on the OTDOA scheme may be performedonly when PRSs are received from at least three eNBs (or cells). When alarge number of eNBs (or cells) transmit PRSs at the same time, thequality of PRSs from at least three eNBs (or cells), from whichpositions are to be measured, may deteriorate due to interference amongthe PRSs transmitted from the eNBs (or cells).

When a muting technology is applied, not all eNBs (or cells) transmitPRSs; instead, some eNBs (or cells) transmit PRSs and the remaining eNBs(or cells) do not transmit PRSs. In this manner, the positioningperformance may be improved.

Whether or not to apply muting associated with an NB-PRS may bedetermined based on a PRS transmission period in the same manner as anLTE PRS. However, in the case of the NB-PRS, the number of subframesused for PRS transmission in a single PRS transmission period is fargreater than that of the LTE PRS. Therefore, this may be inefficient.

As such, a unit for applying muting associated with an NB-PRS needs tobe smaller than an NB-PRS period. The present invention suggests Lsubframes, which have been described in FIGS. 17 to 21, as a unit forapplying muting associated with an NB-PRS.

Applying muting associated with an NB-PRS may be determined based on Lsubframes, which have been described in FIGS. 17-21.

Referring to FIGS. 17-20, whether to apply muting is determined based ona predetermined duration composed of L subframes. In the predeterminedduration composed of L subframes, all of the N_(NB-PRS) subframes(corresponding to subframes including a hatch pattern in thepredetermined duration composed of L subframes in FIGS. 17-20) may ormay not be muted.

As described in FIG. 22, in the case of FIG. 21, whether to apply mutingis determined based on a predetermined duration composed of L subframes.Accordingly, all of the N_(NB-PRS) subframes (subframes having a bitvalue of “1” from among the L subframes including a hatch pattern inFIG. 21) in a predetermined duration composed of L subframes(corresponding to subframes including a hatch pattern of FIG. 21) may ormay not be muted.

A bitmap having a length of k*N_(NB-PRS) _(_) _(rep) may be used toindicate whether muting is to be applied, which is determined based on apredetermined duration composed of L subframes. Muting is not applied toany of the N_(NB-PRS) subframes in a predetermined duration composed ofL subframes where the bit value is “1” in the bitmap having a length ofk*N_(NB-PRS) _(_) _(rep). Muting is applied to all of the N_(NB-PRS)subframes in a predetermined duration composed of L subframes where thebit value of “0”. Conversely, muting is not applied to any of theN_(NB-PRS) subframes in a predetermined duration composed of L subframeswhere the bit value is “0” in the bitmap having a length of k*N_(NB-PRS)_(_) _(rep). Muting is applied to all of the N_(NB-PRS) subframes in apredetermined duration composed of L subframes where the bit value is“1”.

Here, N_(NB-PRS) _(_) _(rep) indicates the number of times that apredetermined period composed of L subframes is repeated within a singleNB-PRS period, as described with reference to FIGS. 17-21.

Also, k indicates the number of NB-PRS periods to which the bitmaphaving a length of k*N_(NB-PRS) _(_) _(rep) (for indicating muting) isapplied.

In this instance, k may be fixed to a predetermined value. For example,k may be fixed to a value (k=1) corresponding to a single NB-PRS period.As another example, k may be fixed to a value (k=2) corresponding to twoNB-PRS periods.

One of a plurality of values may be as k, by higher layer signaling suchas RRC or the like. For example, k may be 1, 2, 4, or 8, whichcorrespond to 1, 2, 4, or 8 NB-PRS periods, one of which may beindicated by higher layer signaling such as RRC or the like. As anotherexample, k may be 2, 4, 8 or 16, which correspond to 2, 4, 8, or 16NB-PRS periods, one of which may be indicated by higher layer signalingsuch as RRC or the like.

A pseudo-random sequence may be used to indicate whether to applymuting, which is determined based on a predetermined duration composedof L subframes.

The value of each sequence element of the pseudo-random sequence may be0 or 1, and each sequence element may correspond to each predeterminedperiod composed of L subframes. In this instance, when the length of thepseudo-random sequence is N, the number of sequence elements is N andeach sequence element may have a value in the range of 0 to N−1, as anindex value.

Muting is not applied to any of the N_(NB-PRS) subframes in apredetermined duration composed of L subframes corresponding to asequence element of “1” in the pseudo-random sequence. Muting is appliedto all of the N_(NB-PRS) subframes in a predetermined duration composedof L subframes corresponding to a sequence element of “0”. Conversely,muting is not applied to any of the N_(NB-PRS) subframes in apredetermined duration composed of L subframes corresponding to asequence element of “0” in the pseudo-random sequence. Muting is appliedto all of the N_(NB-PRS) subframes in a predetermined duration composedof L subframes corresponding to a sequence element of “1”.

In this instance, the pseudo-random sequence may be generated through apseudo-random sequence generator, and the pseudo-random sequencegenerator may be initialized to c_(init) at the start of each period,based on a predetermined period. In this instance, c_(init) may beconfigured based on eNB (or cell)-specific information in order tominimize NB-PRS interference among eNBs (or cells).

A more specific example will be provided as follows. The pseudo-randomsequence may be a pseudo-random sequence which is defined as a length-31gold sequence, and may be expressed as c(i). Here, c(i) may be 0 or 1,which indicates that an i^(th) sequence element, counted from a 0^(th)sequence, has a value of “0” or “1”. In this instance, i={0, 1, . . . ,N_(NB-PRS) _(_) _(rep)−1}. Also, the pseudo-random sequence generatorfor the pseudo-random sequence may be initialized to c_(init) at thestart of each NB-PRS period. In this instance, by taking into accountthat 6 patterns in a single NB-PRS transmission period are determined tobe different by calculating a physical cell ID (PCID) modulo 6, c_(init)may be configured based on an integer value obtained by dividing a PCIDby 6 as shown in Equation 13.

$\begin{matrix}{c_{init} = \left\lfloor \frac{N_{ID}^{cell}}{6} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

FIG. 23 is a flowchart illustrating NB-PRS transmission and receptionoperations according to the present invention.

In operation S2310, an eNB may recognize an NB-PRS configuration of anNB-PRS to be transmitted to a UE. In this instance, the NB-PRSconfiguration of an NB-PRS to be transmitted from each eNB to a UE maybe determined by a location server as shown in FIG. 11, and each eNB mayreceive an indication from the location server. As described in theexamples of the present invention, the NB-PRS configuration may includeone or more of an RE pattern in an NB-PRS transmission subframe, anNB-PRS sequence, an NB-PRS transmission PRB configuration, and an NB-PRStransmission subframe configuration.

In operation S2320, the eNB transmits NB-PRS configuration-relatedinformation to the UE. The NB-PRS configuration-related information maybe indicated to each eNB through higher layer signaling (e.g., LPP layersignaling from the location server), and the eNB may then provide thesame to the UE. The NB-PRS configuration-related information may includeinformation associated with the NB-PRS transmission subframeconfiguration. The information associated with the NB-PRS transmissionsubframe configuration may include one or more of: an NB-PRS offset; anNB-PRS period; a value N_(NB-PRS) that indicates the number of NB-PRStransmission subframes; information indicating a predetermined subframe(e.g., an NB-PRS non-transmission subframe) in which an NB-PRS is nottransmitted; a bitmap indicating NB-PRS transmission subframes; a valueL which indicates the number of subframes that form a predeterminedduration in an NB-PRS period; and a value N_(NB-PRS) _(_) _(rep) thatindicates the number of times a predetermined duration composed of Lsubframes is repeated. Also, previously determined values are used forsome of the information associated with the NB-PRS transmission subframeconfiguration. In this instance, it is determined that a UE is alreadyaware of the values without separate signaling. Detailed descriptions ofeach piece of information, which have already been included referring tothe examples in FIGS. 14-21, will be omitted.

In operation S2330, the eNB transmits an NB-PRS to the UE. The UE mayrecognize one or more of the RE pattern in an NB-PRS transmissionsubframe, the NB-PRS sequence, the NB-RS transmission PRB configuration,and the NB-PRS transmission subframe configuration based on the NB-PRSconfiguration information received in operation S2320. The UE may thenattempt to receive an NB-PRS based on this recognition.

In operation S2340, the UE generates positioning information (e.g.,information such as RSTD, which is used for determining the location ofthe UE itself), using the NB-PRS received from the eNB and NB-PRSsreceived from other eNBs.

In operation S2350, the UE transmits the positioning informationgenerated in operation S2340 to the eNB or to an NB-IoT server (orlocation server) via the eNB.

Although the above described illustrative methods are expressed as aseries of operations for ease of description, they do not limit theorder of operations executed; the operations may also be executed inparallel or in a different order. In addition, all of the operationsdescribed above may not always be required to implement the method ofthe present invention.

The embodiments described above include examples of various aspects ofthe present invention. Although it is difficult to describe all thepossible combinations showing the various aspects, it is apparent tothose skilled in the art that other combinations are possible.Therefore, it should be construed that the present invention includesother substitutions, corrections, and modifications belonging within thescope of claims.

The scope of the present invention may include an apparatus forprocessing or implementing the operations according to variousembodiments of the present invention.

In one or more embodiments, an NB UE processes a positioning referencesignal. The NB UE receives NB positioning reference signal (PRS)configuration information configured for the NB UE, the NB PRSconfiguration information comprising an NB PRS bitmap indicating apattern selecting NB PRS subframes. Each NB PRS subframe comprises an NBPRS for positioning the NB UE. The NB UE determines, based on the NB PRSbitmap, a first NB PRS mapped in NB PRS subframes of an NB PRS referencecell, determines, based on the NB PRS bitmap, a second NB PRS mapped inNB PRS subframes of an NB PRS neighbor cell. The NB UE generates, basedon the first NB PRS and the second NB PRS, a reference signal timedifference (RSTD) measurement, and transmits the RSTD measurement.

The NB PRS bitmap may have a size of 10 consecutive bits respectivelycorresponding to 10 subframes in each radio frame. The NB UE maydetermine, from a plurality of radio frames of the NB PRS reference celland based on a plurality of repetitions of the NB PRS bitmap, the NB PRSsubframes of the NB PRS reference cell.

The NB UE may determine, from a plurality of radio frames of the NB PRSneighbor cell and based on a plurality of repetitions of the NB PRSbitmap, the NB PRS subframes of the NB PRS neighbor cell. The NB UE maydetermine, based on value ‘1’ assigned to n-th bit of the NB PRS bitmap,n-th subframe of a radio frame as one NB PRS subframe.

The NB UE may calculate, based on a receipt time difference between thefirst NB PRS and the second NB PRS, a first RSTD. The NB UE maydetermine a third NB PRS mapped in NB PRS subframes of a second NB PRSneighbor cell, and calculate, based on a receipt time difference betweenthe first NB PRS and the third NB PRS, a second RSTD. The NB UE maygenerate, based on the first RSTD and the second RSTD, the RSTDmeasurement.

The NB UE may receive a physical resource block (PRB) index indicatingone PRB, and determine a frequency band corresponding to the one PRB andassigned to the NB UE. The first NB PRS and the second NB PRS are mappedin the frequency band.

The NB UE may receive an NB PRS muting indicator. The NB PRS mutingindicator has a size of k consecutive bits respectively corresponding tok consecutive radio frames, where k is an integer selected from 2, 4, 8,or 16. The NB PRS bitmap may have a size of 10 consecutive bitsrespectively corresponding to 10 subframes in each radio frame.

The NB UE may determine, based on a value of n-th bit of the NB PRSmuting indicator, whether NB PRS subframes in n-th radio frame of the kconsecutive radio frames are muted.

In one or more embodiments, a network including a base station mayprocess a positioning reference signal. The network may determine anarrow-band (NB) positioning reference signal (PRS) bitmap indicating apattern selecting NB PRS subframes. Each NB PRS subframe comprises an NBPRS for positioning an NB user equipment (UE). The network transmits, tothe NB UE, NB PRS configuration information for the NB UE, the NB PRSconfiguration information comprising the NB PRS bitmap. A reference cell(e.g., an NB PRS reference cell) determines, based on the NB PRS bitmap,NB PRS subframes of the reference cell, and map a first NB PRS in the NBPRS subframes of the reference cell. The reference cell receives, fromthe NB UE and in response to the first NB PRS, a reference signal timedifference (RSTD) measurement.

A neighbor cell (e.g., an NB PRS neighbor cell) may determine, based onthe NB PRS bitmap, NB PRS subframes of the neighbor cell, and map a ndNB PRS in the NB PRS subframes of the neighbor cell. The RSTDmeasurement is further based on the second NB PRS.

The NB PRS bitmap may have a size of 10 consecutive bits respectivelycorresponding to 10 subframes in each radio frame.

The reference cell may determine, from a plurality of radio frames ofthe reference cell and based on a plurality of repetitions of the NB PRSbitmap, the NB PRS subframes of the reference cell. The network mayassign value ‘1’ to n-th bit of the NB PRS bitmap to designate n-thsubframe of a radio frame as one NB PRS subframe.

The network may transmit, to the NB UE, an NB PRS muting indicator. TheNB PRS muting indicator may have a size of k consecutive bitsrespectively corresponding to k consecutive radio frames, and may selectan integer value for k from 2, 4, 8, or 16. The reference cell and oneor more neighbor cells may mute, based on a value of n-th bit of the NBPRS muting indicator, NB PRS subframes in n-th radio frame of the kconsecutive radio frames.

FIG. 24 is a diagram illustrating the configuration of a processor of awireless device according to the present invention.

The processor 210 of the eNB 200 may be configured to implement theoperations of the eNB, which have been described for all of theembodiments of the present invention.

For example, the higher layer processing unit 211 of the processor 210of the eNB 200 may include an NB-PRS configuration recognizing unit 2440and an NB-PRS configuration-related information generating unit 2450.The eNB may recognize the NB-PRS configuration of an NB-PRS to betransmitted to a UE through the NB-PRS configuration recognizing unit2440. In this instance, the NB-PRS configuration of an NB-PRS to betransmitted from each eNB to a UE may be determined by a location serveras shown in FIG. 11, and each eNB may receive an indication from thelocation server. As described in the examples of the present invention,the NB-PRS configuration may include one or more of an RE pattern in anNB-PRS transmission subframe, an NB-PRS sequence, an NB-PRS transmissionPRB configuration, and an NB-PRS transmission subframe configuration.The eNB may generate information related to the NB-PRS configuration ofan NB-PRS to be transmitted to the UE, through the NB-PRSconfiguration-related information generating unit 2450. The NB-PRSconfiguration-related information may be indicated to each eNB throughhigher layer signaling (e.g., LPP layer signaling from the locationserver), and the eNB may generate the information to be transmitted tothe UE based on the indication information. The NB-PRSconfiguration-related information may include information associatedwith the NB-PRS transmission subframe configuration. The informationassociated with the NB-PRS transmission subframe configuration mayinclude one or more of: an NB-PRS offset; an NB-PRS period; a valueN_(NB-PRS) which indicates the number of NB-PRS transmission subframes;information indicating a predetermined subframe (e.g., an NB-PRSnon-transmission subframe) in which an NB-PRS is not transmitted; abitmap indicating NB-PRS transmission subframes, a value L whichindicates the number of subframes that form a predetermined duration inan NB-PRS period, and a value N_(NB-PRS) _(_) _(rep) which indicates thenumber of times that a predetermined duration composed of L subframes isrepeated.

The physical layer processing unit 212 of the processor 210 of the eNB200 may include an NB-PRS transmitting unit 2460. The NB-PRStransmitting unit 2460 may map an NB-PRS onto a physical resourceaccording to the NB-PRS configuration, and may transmit the same to theUE 100.

The processor 110 of the UE 100 may be configured to implement theoperations of the UE, which have been described in all of theembodiments of the present invention.

For example, the higher layer processing unit 111 of the processor 111of the UE 100 may include an NB-PRS configuration recognizing unit 2410and a positioning information generating unit 2420. The physical layerprocessing unit 112 of the processor 110 of the UE 100 may include anNB-PRS receiving unit 2430.

Based on the NB-PRS configuration-related information provided from theeNB 200, the NB-PRS configuration recognizing unit 2410 may recognizeone or more configurations of: an RE pattern in an NB-PRS transmissionsubframe, an NB-PRS sequence, an NB-PRS transmission PRB configuration,and an NB-PRS transmission subframe configuration.

The NB-PRS receiving unit 2430 may receive an NB-PRS in a physicalresource based on the determined NB-PRS configuration.

The positioning information generating unit 2420 may generatepositioning information based on the received NB-PRS, and may transmitthe same to an eNB or a network-side server through the physical layerprocessing unit 112.

What is claimed is:
 1. A narrow-band (NB) user equipment (UE)comprising: a transceiver to receive NB positioning reference signal(PRS) configuration information configured for the NB UE, the NB PRSconfiguration information comprising: an NB PRS bitmap indicating apattern selecting NB PRS subframes, wherein each NB PRS subframecomprises an NB PRS for positioning the NB UE; and a processor todetermine, based on the NB PRS bitmap, a first NB PRS mapped in NB PRSsubframes of an NB PRS reference cell, to determine, based on the NB PRSbitmap, a second NB PRS mapped in NB PRS subframes of an NB PRS neighborcell, and to generate, based on the first NB PRS and the second NB PRS,a reference signal time difference (RSTD) measurement, wherein thetransceiver transmits the RSTD measurement.
 2. The NB UE of claim 1,wherein the NB PRS bitmap has a size of 10 consecutive bits respectivelycorresponding to 10 subframes in each radio frame.
 3. The NB UE of claim2, wherein the processor is configured to determine, from a plurality ofradio frames of the NB PRS reference cell and based on a plurality ofrepetitions of the NB PRS bitmap, the NB PRS subframes of the NB PRSreference cell.
 4. The NB UE of claim 2, wherein the processor isconfigured to determine, from a plurality of radio frames of the NB PRSneighbor cell and based on a plurality of repetitions of the NB PRSbitmap, the NB PRS subframes of the NB PRS neighbor cell.
 5. The NB UEof claim 2, wherein the processor is configured to determine, based onvalue ‘1’ assigned to n-th bit of the NB PRS bitmap, n-th subframe of aradio frame as one NB PRS subframe.
 6. The NB UE of claim 1, wherein theprocessor is configured to calculate, based on a receipt time differencebetween the first NB PRS and the second NB PRS, a first RSTD.
 7. The NBUE of claim 6, wherein the processor is configured to: determine a thirdNB PRS mapped in NB PRS subframes of a second NB PRS neighbor cell; andcalculate, based on a receipt time difference between the first NB PRSand the third NB PRS, a second RSTD.
 8. The NB UE of claim 7, whereinthe generating the RSTD measurement comprises: generating, based on thefirst RSTD and the second RSTD, the RSTD measurement.
 9. The NB UE ofclaim 1, wherein: the transceiver receives a physical resource block(PRB) index indicating one PRB; and the processor is configured todetermine a frequency band corresponding to the one PRB and assigned tothe NB UE, wherein the first NB PRS and the second NB PRS are mapped inthe frequency band.
 10. The NB UE of claim 1, wherein the transceiverreceives an NB PRS muting indicator, wherein the NB PRS bitmap has asize of 10 consecutive bits respectively corresponding to 10 subframesin each radio frame, and wherein the NB PRS muting indicator has a sizeof k consecutive bits respectively corresponding to k consecutive radioframes, where k is an integer selected from 2, 4, 8, or
 16. 11. The NBUE of claim 10, wherein the processor is configured to determine, basedon a value of n-th bit of the NB PRS muting indicator, whether NB PRSsubframes in n-th radio frame of the k consecutive radio frames aremuted.
 12. A system comprising: a processor to determine a narrow-band(NB) positioning reference signal (PRS) bitmap indicating a patternselecting NB PRS subframes, wherein each NB PRS subframe comprises an NBPRS for positioning an NB user equipment (UE); and a transceiver totransmit, to the NB UE, NB PRS configuration information for the NB UE,the NB PRS configuration information comprising the NB PRS bitmap,wherein the processor is configured to determine, based on the NB PRSbitmap, NB PRS subframes of a reference cell, and to map a first NB PRSin the NB PRS subframes of the reference cell, and wherein thetransceiver receives, from the NB UE and in response to the first NBPRS, a reference signal time difference (RSTD) measurement.
 13. Thesystem of claim 12, further comprising: one or more computing devices ofa neighbor cell configured to: determine, based on the NB PRS bitmap, NBPRS subframes of the neighbor cell; and map a second NB PRS in the NBPRS subframes of the neighbor cell, wherein the RSTD measurement isfurther based on the second NB PRS.
 14. The system of claim 12, whereinthe NB PRS bitmap has a size of 10 consecutive bits respectivelycorresponding to 10 subframes in each radio frame.
 15. The system ofclaim 14, wherein the processor is configured to determine, from aplurality of radio frames of the reference cell and based on a pluralityof repetitions of the NB PRS bitmap, the NB PRS subframes of thereference cell.
 16. The system of claim 14, wherein the processor isconfigured to assign value ‘1’ to n-th bit of the NB PRS bitmap todesignate n-th subframe of a radio frame as one NB PRS subframe.
 17. Thesystem of claim 14, wherein the transceiver transmits, to the NB UE, anNB PRS muting indicator, wherein the NB PRS muting indicator has a sizeof k consecutive bits respectively corresponding to k consecutive radioframes, where k is an integer selected from 2, 4, 8, or
 16. 18. Thesystem of claim 17, wherein the processor is configured to mute, basedon a value of n-th bit of the NB PRS muting indicator, NB PRS subframesin n-th radio frame of the k consecutive radio frames.